Instant adhesive composition utilizing calixarene accelerators

ABSTRACT

Cyanoacrylate adhesive compositions which employ calixarene compounds as additives give substantially reduced fixture and cure times on de-activating substrates such as wood. The calixarene compounds are preferably employed at levels of about 0.1-1% by weight of the composition. The calixarene compounds particularly useful in this invention may be represented by the formula: ##STR1## where R 1  is alkyl, alkoxy, substituted alkyl or substituted alkoxy; R 2  is H or alkyl; and n=4, 6, or 8. 
     The compositions are further characterized by a thickener component, which may suitably be selected from various polymers such as poly(methyl methacrylate), methacrylate type copolymers, acrylic rubbers, polyvinyl acetate and poly(α-cyanoacrylate) or silicas treated with polydialkylsiloxanes or trialkylsilanes.

This application is a division of Ser. No. 673,621, filed Nov. 21, 1984,now U.S. Pat. No. 4,556,700, which is a continuation-in-part of Ser. No.575,257, filed Jan. 30, 1984 now abandoned.

BACKGROUND OF THE INVENTION

In DE-OS No. 2,816,836, dated Oct. 26, 1978 there are describedcyanoacrylate adhesive compositions which employ crown ethers aspolymerization accelerators. Such compositions are useful for bondingacidic surfaces such as wood which inhibit cyanoacrylate polymerization.

Crown ethers, however, are known to be very toxic, the reported effectsof exposure including damage to the central nervous system andtesticular atrophy. Leong, B. K. J., Chem. Eng. News, 53, 5(1975).Furthermore, such accelerators are reportedly very difficult tosynthesize, supplying the desired product in only low yields because ofthe tendency to produce intermolecular linkages. Accordingly, there is aneed for alternative cyanoacrylate accelerators suitable for woodbonding applicators.

In U.S. Pat. No. 4,170,585, there are described cyanoacrylatecompositions in which certain polyethylene glycols or poly(ethyleneoxy)functional surfactants act as wood bonding accelerators. Such compounds,however, have the reported disadvantage that they tend to contain waterand other difficult to remove substances which spontaneously initiatepolymerization of the cyanoacrylate monomer.

U.S. Pat. No. 4,377,490 discloses mixtures of aromatic and aliphaticpolyols and polyethers said to improve initial strength of cyanoacrylatewood bonding products.

U.S. Pat. No. 4,386,193 discloses certain 3 or 4 arm polyol podandcompounds as alternatives to crown-ether accelerators.

Japan Kokai Tokkyo Koho 82-70171, suggests the use of certainpolyorganosiloxane compounds which include polyether substituents asadditives for wood bonding cyanoacrylate compositions.

Chem. Abstracts, 97 145913n reports the use of a hydroxy-terminatedpoly(dimethylsiloxane) in fast bonding cyanoacrylate compositions.

DE-OS 3,006,071 discloses certain furan derivatives as co-acceleratorswith crown ethers in cyanoacrylate compositions.

SUMMARY OF THE INVENTION

The present invention is a new cyanoacrylate composition for bondingwood and other de-activating surfaces such as leather, ceramic, plasticsand metals with chromate treated or acidic oxide surfaces. The inventivecompositions are standard cyanoacrylate adhesive formulations to whichhave been added, as accelerators, certain calixarene compounds stable tocyanoacrylate monomers. The calixarene compounds are preferably employedat levels between about 0.1% and 1% by weight of the composition.

The calixarene compounds particularly useful in the invention may berepresented by the formula: ##STR2## where R¹ is alkyl, alkoxy,substituted alkyl or substituted alkoxy; R² is H or alkyl; and n=4, 6,or 8.

DETAILED DESCRIPTION OF THE INVENTION

The α-cyanoacrylate-type adhesive composition of this invention asdescribed above contains an α-cyanoacrylate monomer of the formula:##STR3## wherein R³ represents a straight chain or branched chain alkylgroup having 1 to 12 carbon atoms (which may be substituted with asubstituent such as a halogen atom or an alkoxy group) a straight chainor branched chain alkenyl group having 2 to 12 carbon atoms, a straightchain or branched chain alkynyl group having 2 to 12 carbon atoms, acycloalkyl group, an aralkyl group or an aryl group. Specific examplesof the groups for R³ are a methyl group, an ethyl group, an n-propylgroup, an isopropyl group, an n-butyl group, an isobutyl group, a pentylgroup, a hexyl group, an allyl group, a methallyl group, a crotyl group,a propargyl group, a cyclohexyl group, a benzyl group, a phenyl group, acresyl group, a 2-chloroethyl group, a 3-chloropropyl group, a2-chlorobutyl group, a trifluoroethyl group, a 2-methoxyethyl group, a3-methoxybutyl group and a 2-ethoxyethyl group. Ethyl cyanoacrylate isthe preferred monomer for use in the inventive compositions.

A single α-cyanoacrylate monomer or a mixture of two or more of theseα-cyanoacrylate monomers can be used. Generally, the aboveα-cyanoacrylate monomer alone is not sufficient as an adhesive, and thecomponents set forth below are sometimes added.

(1) An anionic polymerization inhibitor

(2) A radical polymerization inhibitor

(3) A thickener

(4) Special additives such as plasticizers and heat stabilizers

(5) Perfumes, dyes, pigments, etc.

A suitable amount of the α-cyanoacrylate monomer present in the adhesivecomposition is about 80 to 99.9% by weight, preferably 90 to 99.9% byweight, based on the total weight of the adhesive composition.

An anionic polymerization inhibitor is added to the α-cyanoacrylate-typeadhesive composition, e.g., in an amount of about 1 to 1000 ppm based onthe total weight of the adhesive composition, to increase the stabilityof the adhesive composition during storage, and examples of knowninhibitors are sulfur dioxide, aromatic sulfonic acids, aliphaticsulfonic acids, sultones, and carbon dioxide.

Suitable examples of radical polymerization inhibitors include, forexample, hydroquinone and hydroquinone monomethyl ether. A radicalpolymerization inhibitor is added, e.g., in amount of about 1 to 5000ppm based on the total weight of the adhesive composition, for thepurpose of capturing radicals which are formed by light during storage.

A thickener is added to increase the viscosity of theα-cyanoacrylate-type adhesive composition. The α-cyanoacrylate monomergenerally has a low viscosity of about several centipoises, andtherefore, the adhesive penetrates into porous materials such as woodand leather or adherends having a rough surface. Thus, good adhesionstrengths are difficult to obtain. Various polymers can be used asthickeners, and examples include poly(methyl methacrylate),methacrylate-type copolymers, acrylic rubbers, cellulose derivatives,polyvinyl acetate and poly(α-cyanoacrylate). A suitable amount ofthickener is generally about 20% by weight or less based on the totalweight of the adhesive composition.

As disclosed in the copending application of Alan Litke, Ser. No.528,275, filed Aug. 31, 1983, now U.S. Pat. No. 4,477,607 certain fumedsilica fillers treated with polydialkylsiloxanes or trialkylsilanes mayalso be usefully employed as cyanoacrylate thickeners.

The plasticizers, perfumes, dyes, pigments, etc., may be added dependingon use purposes in amounts which do not adversely affect the stabilityof the α-cyanoacrylate monomer. The use of such additives is within theskill of those practicing in the cyanoacrylate adhesive art and need notbe detailed herein.

Calixarene compounds are known and may be readily synthesized by methodsdescribed in C. Gutsche, Acc. Chem. Res., 16, 161-170 (1983), andreferences cited therein, the appropriate disclosures of which areincorporated herein by reference. Synthesis methods for the calixarenecompounds which are preferred for use in the invention are exemplifiedin Examples 1 and 2 herein. The preferred compounds may be representedby formula I wherein R¹ is OC₂ H₅, R² is H or t-butyl and n=4 or 6.Other suitable compounds include those of formula I where R¹ is methoxyor methyl.

The invention may be further understood with reference to the followingnon-limiting examples.

EXAMPLE 1 Synthesis of 37,38,39,40,41,42-hexa-(2-oxo-2-ethoxyl)-exthoxycalix [6] arene

In a 1-liter flask equipped with a Dean-Stark trap, 30 grams ofpara-tert-butyl phenol, 12 grams of paraformaldehyde, 18 mls of a 5Naqueous solution of rubidium hydroxide and 300 mls of xylene wererefluxed for 5 hours. The cooled precipitate was filtered and suspendedin 900 mls of chloroform and washed with 300 mls of 1N aqueous solutionof hydrochloric acid. The organic layer was separated, washed withwater, dried over magnesium sulfate, and concentrated to 300 mls.Methanol was added to yield a precipitate which represented a 52% yieldof hexamer.

A mixture of 6.48 grams of hexamer and excess sublimed aluminum chloridewas stirred overnight in dry toluene under a nitrogen atmosphere. Waterwas added to destroy the excess aluminum chloride and toluene wasremoved on a rotary evaporator. The crude orange oil was dissolved in300 ml dichloromethane and washed with dilute acid followed by water toremove inorganic salts. The dichloromethane was removed under reducedpressure and diethyl ether added to the residue. A precipitate wascollected, filtered and washed with ether. The remaining powderrepresented an 88% yield.

This powder (3.75 grams) was added to 8 mls of ethyl bromoacetate andexcess potassium carbonate and refluxed in dry acetone for 48 hours.Removal of solvent and washing with water produced a 78% yield of crudeproduct. Recrystallization from a benzene/petroleum ether mixtureyielded white crystals. Analysis: Calculated, C: 68.75%, H: 6.25%;Found, C: 66.61%, H: 6.28%. NMR: ¹ H(CDCl₃), δ=6.75 multiplet, 3H,δ=4.2, 4.05, multiplet, 6H, δ=1.2, triplet, 3H.

EXAMPLE 2

25,26,27,28-Tetra-(2-oxo-2-ethoxy)-ethoxy calix [4] arene was preparedby an analogous procedure, using sodium hydroxide in place of rubidiumhydroxide in the first step.

EXAMPLE 3

To a commercially available cyanoacrylate-based adhesive (Loctite 495,sold by Loctite Corporation, Newington, Conn.) 0.1% by weight of37,38,39,40,41,42-hexa-(2-oxo-2-ethoxy)-ethoyx calix [6] arene (HECA)was added. White deal wood lap shears were bonded on a 1.25 cm overlapwith the compositions and fixture times measured. Fixture time was takenas the time at which the bond was no longer separable by hand. Theuntreated 495 adhesive gave a fixture time of between 20 and 25 minutes.The adhesive containing 0.1% HECA gave a fixture time of between 3 and 5minutes. The HECA-containing composition exhibited storability ofgreater than 48 hours at 82° C.

EXAMPLE 4

The test in Example 3 was repeated using ramin wood lap shears as thesubstrates. The untreated 495 adhesive gave a fixture time of 45-55seconds. The adhesive containing 0.1% HECA gave a fixture time 5-10seconds.

EXAMPLE 5

The test in Example 3 was repeated using25,26,27,28-Tetra-(2-oxo-2-ethoxy)-ethoxy calix [4] arene (TECA) as anadditive to Loctite 495. The adhesive containing 0.1% TECA gave afixture time of 5-10 minutes. Adhesive containing 1.0% TECA gave afixture time of 5 minutes.

EXAMPLE 6

Leather lap shears were bonded with adhesive compositions and fixturetimes were measured. Loctite 495 adhesive gave a fixture time of 5-6minutes. Adhesive containing 0.1% HECA gave a fixture time of 2-21/2minutes. Adhesive containing 0.1% TECA gave a fixture time of 11/2-2minutes.

EXAMPLE 7

The test in Example 3 was repeated using5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-(-2-oxo-2-ethoxy)-ethoxycalix [8] arene (OECA) as an additive to Loctite 495. The adhesivecontaining 0.1% OECA gave a fixture time of 10 minutes. Adhesivecontaining 1.0% OECA gave a fixture time of 5-10 minutes.

EXAMPLE 8 Synthesis of5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-oxo-2-ethoxy)-ethoxycalix [4] arene

A mixture of 1.62 g of 5,11,17,23,-tetra-tert-butyl-25,26,27,28-calixtetrahydroxy [4] arene, 3.34 g ethyl bromoacetate, 2.07 g anhydrouspotassium carbonate, and 50 milliters of dry acetone was refluxed undernitrogen for 14 days. At the end of this time the mixture was pouredinto 250 milliters of a 10% solution of aqueous hydrochloric acid. Theprecipitated solid was filtered, washed with distilled water and driedovernight at 55° C. to yield 2.4 g of crude product. Recrystallizationof this material from hot ethanol gave 1.35 g of a colorless crystallineproduct which was characterized by i.r. and n.m.r. spectroscopy andcrystallography as5,11,17,13-tetra-tert-butyl-25,26,27,28-tetra-(2,oxo-2-ethoxy)-ethoxycalix [4] arene (M.Pt.=150°-151° C.).

We claim:
 1. In a cyanoacrylate adhesive composition, the improvementcomprising that the composition includes a thickener in an amount ofabout 20% or less by weight of the composition and an acceleratorcompound in a conventional amount, the thickener selected from the groupconsisting of poly(methyl methacrylate); methacrylate type copolymers;acrylic rubbers; polyvinyl acetate; poly(α-cyanoacrylate); and fumedsilica fillers treated with polydialkylsiloxanes or trialkylsilanes andthe accelerator being a calixarene compound stable to cyanoacrylatemonomers represented by the formula: ##STR4## where R¹ is alkyl, alkoxy,substituted alkyl or substituted alkoxy; R² is H or alkyl; and n=4, 6 or8.
 2. The composition of claim 1 wherein R¹ is OCH₂ CH₃.
 3. Thecomposition of claim 1 wherein R² is H and n=4 or
 6. 4. The compositionof claim 1 wherein R² is t-butyl.
 5. The composition of claim 1 whereinthe cyanoacrylate adhesive composition contains a monomer of theformula: ##STR5## wherein R³ represents a substituted or unsubstitutedstraight chain or branched chain alkyl group having 1 to 12 carbonatoms, a straight chain or branched chain alkenyl group having 2 to 12carbon atoms, a straight chain or branched chain alkynyl group having 2to 12 carbon atoms, a cycloalkyl group, an aralkyl group or an arylgroup.
 6. The composition of claim 1 wherein said calixarene compound ispresent in the range of 0.1-1% by weight of the composition.
 7. Thecomposition of claim 1 further comprising an anionic polymerizationinhibitor and a free radical polymerization inhibitor.
 8. A compositionas in claim 1 where the thickener is a polymer selected from the groupconsisting of poly(methyl methacrylate), methacrylate-type copolymers,acrylic rubbers, polyvinyl acetate and poly(α-cyanoacrylate).
 9. Acomposition as in claim 1 wherein the thickener is a fumed silica fillertreated with polydialkylsiloxanes or trialkylsilanes.